Internal combustion engines known in the art include various combustion chamber configurations. Some combustion chamber configurations include passive pre-chamber and fuel fed pre-chamber configurations. Pre-chamber configurations are particularly useful for initiating and propagating the combustion flame for lean-burn natural gas engines. Some alternative fuels, such as natural gas, can be difficult to ignite using conventional open chamber type combustion chamber configurations. Some pre-chambers make it is possible to run the engine at much leaner air-to-fuel ratios enabling the engine to meet lower emissions more fuel efficiently. But with ever increasing power density targets, it becomes a challenge to meet these requirements at acceptable combustion stability.
Pre-chambers include a combustion volume in which a spark plug is located. The combustion volume of the pre-chamber is linked to a main combustion chamber by the use of one or more orifices. The spark plug initiates a combustion event by generating a spark (e.g., electron current). More specifically, the spark from the spark plug initiates a flame that propagates through the pre-chamber volume. This combustion creates a sudden increase in pressure in the pre-chamber creating a large pressure difference across the orifices between the pre-chamber and main chamber. The pressure difference forces the flame to propel through the orifices into the main combustion chamber resulting in a successful combustion event.
After a successful combustion event, the residual exhaust gases in the main chamber are scavenged during the exhaust stroke. During a subsequent intake stroke, fresh air and fuel are introduced into the main chamber via a compression event driven by a piston. During the subsequent compression stroke, the pressure difference between the main chamber and pre-chamber increases forcing the air and fuel through the orifices into the pre-chamber. In alternative configurations, fresh air may be introduced directly into the pre-chamber during the intake stroke and/or fuel may be injected into the pre-chamber during the intake stroke and/or subsequent compression stroke.